Drilling fluid and the method of drilling and lubricating wells



Patented Sept. 21, 1943 UNlTED STAT-ES, PATENT OFFICE panama FLUID AND'rrm nm'rnon or panama AND women-ruse wens Baruch Cerf, LosAngeles,Callf asslgnor to Graphite Frees Company, Los Angeles, Calif.

No Drawing. Application March 14, 1941,

. Serial No. 383,351

This invention concerns the treatment and lubrication of equipment andtools in the drilling ,of wells and the like, and especially for oil andgas wells, and also the treatment, improvement and conditioning of thecirculating fluid, or circulating mud for such wells when earthymaterials are suspended in the fluid. For instance, in rotary drilling,mud-laden fluids, or clay-laden fluids, of various nature are introducedto the upper end of the drill stem or pipe under pressure and made toflow to the drill bit where it issues and then passes between the drill'stem and hole bore to the ground surface for cleaning and inspection. v

Some of the purposes of the circulating fluid, regardless of .the exactingredients therein, is to remove the cuttings from the hole, providesome lubrication for the bit and stem, prevent freezing or sticking ofthe bit and stem in the 'hole, reduces gas and other pressures in thehole, and provide a mud-liner, when mud is an ingredient, for the holeso as to avoid liquid absorption along its walls, and reduce cave inhazards, shale slides, etc.

So far as known, there has not been any satisfactory method or means forlubricating'the drilling bit or its connected stem and parts while inthe hole and at work. Various suspensoids have been tried in themud-laden circulatory fluid to make it slick, soapy, etc., so as toreduce friction as much as possible, but a truly effective lubricantwith a high degree of wear reducing qualities has not been put topractical use. Many well known lubricants have proven more or lessdetrimental to the required qualities demanded of the mud, :the requiredqualities of which could not be sacrificed in favor of a betterlubricant.

I have discovered that carbon allotr P raphite and allotroplc forms ofcarbon added to the mud-laden fluid solved the problem of lubricationand also assisted certain functions of the mud. It was found that thecarbon additive not only greatly reduced the destructive attrition andabrasion of the bits and stems used in. drilling, but aflordedstableprotection for all the equipment used which came into contact with thecarbo-mud fluid, whether in storage or in the outdoor working pipestacks. This inventive fluid made it possible to increase the speed ofthe moving equipment, especially rotary bits resulting in the drillingof larger and deeper bores, and the use of longer casingsand drillpipes. Furthermore, the addition of allotroplc carbon to the mudincreased the effectiveness of the drill upon the harder formationalstrata, gave the mud-fluid under the higher pressures and "temperaturesencountered at great depths. The

preferred forms of carbon for best results will be revealed later. It isto be understood, that all wells do not necessarily employ a clay baseddrilling fluid or one which contains earthy materials as the circulatorydrilling medium, that such circulatory drilling fluid may be oil based,or oil-water-clay based, and when so oil based,

the fluid may or may not contain earthy mate rials except such earthymaterials which may incidentally be entrained in the fluid while it iscirculated in the well.

One of the principal objects of this invention is to economicallyprovide new mud-laden circulating fluids for the drilling of wells whichprovide continuous lubrication to all the moving partsof the drillingequipment and especially to the cones or cutters, their bearing supportsand races within the drill hit, all discs and bearings, reamers, stems,and the-formation cutterr drillpipe, bit and easing surfaces necessaryto discourage high-speed power losses, lessen torque,

stresses and prevents frictional heating ingeneral.

A-further object is to present the means and methods of improving thecirculatory mud-fluids in the drilling of wells and for imparting to themud-fluids new and useful functions without increased costs or theemployment of additional equipment.

A still further object of this invention is to I present the means,products, and methods for description, the foregoing preamble and thecarrying out the intent and purposes of this invention. I

Other objects, advantages and features of my invention will appear fromreading the following appended claims; a

Applicant is about to disclose one or more forms in which the inventioncan be practiced,

but it is to be understood that this invention is ,susceptlble ofvariousother embodiments and that theinventlon is not to be limited inany manner whatsoever, except as limited by the appended claims.

Both the mined and manufactured varieties of graphite possess importantlubricating properties. Carbon allotrope graphites are valuable for manydiversified uses in industry, and as I have discovered. it is ofincalculable value to the industry of drilling oil and gas wells for thelubricating and protection of the sub-surface equipment at any and alldeaths.

The properties of graphite differ widely from those of amorphous carbonwhich has a minimum of lubricating and friction reducing values, and isnot comparable to the attributes of graphite or is it ever used as asubstituent where graphite is required. Graphite mined and manufactured,(imported and domestic or native) is used in many industries and formany purposes. Selected graphites allocated commercially as #lubrieatinggraphite" or "for lubricating purposes has high graphitic carboncontent, is free from grit and abrasive matter, and has a profoundinherent aflinity for metal surfaces and ability to penetrate to andremain at points inaccessible to other lubricants. This graphite islubricous and has a highly unctuous value of .major importance as afriction reducer. Such a graphite is valuable in this invention.

It is because of its greasy feel, unctuousness and non-coalescent naturethat the carbon allotrope graphite is preferred as an additive formud-laden fluids. Its suitability as a dry lubricant has long beenrecognized and is often designated a slick to which nothing sticks." Itis a solid, chemically inert, highly resistant to oxidation, and stableunder conditions that. are deof the graphite used is not of primaryimportwice. The graphitic carbon content may vary in quantity and puritybut should conform to graphite allotted and designated to conform to therequirements of "commercial lubricating graphite.

The exact degree or mesh, measured by riddle, screen, or air float, offineness of graphite or variant in size of the particles is not ofprimary structive to fluid and semi-solid lubricants as well aspreventive petro-base coatings.

Graphite orients itself easily to metal surfaces and thereby createswhat is known as a "slick graphoid siu'face on the metal. particlesbecome intimately combined with the metal of the surface, and this is adesirable attribute since the lubric graphoid surface provides a perfectdry solid lubrication. It has an antisticking quality and an extremelylow co-eflicient of friction and acts as a boundary film between thefast rising swirling helical drilling fluid and the faster rotatingdrill stem. power loss with the additional advantage of resistance tocorrosion from drilling chemicals or oxidation by weathering. Thegraphoid surface consists of a plane of carbon allotrope graphiteparticles adhering firmly to the metal surface,

tightly linked together and correlated to the finer graphite particlesoccluded within the pores of the metal, filling in the depressions andlevelling the projections of the roughness of the metal surfaces. Theseentrapped absorbed graphite particles explains the self-lubricatingproperties of metal so treated and the ability of metal so treated-torun without damage or injury for a considerable period of time, evenafter a breach or rupture, caused by exceptional conditions, exposes themetal surface. This lubricating quality lasts until restored by theexternal source of graphite, circulating with the mild through the boreof the well, reaches all parts to renew their surfaces.

,The graphite used may be natural or artifical of the various gradesavailable which have lubricating values, or by selective or blending ofone The graphite It discourages or more types of carbon or distinctiveallotropic importance, but a substantial portion of them should comewithin the particle size range generally designated as 200 mesh orfiner.

Also, the proportions of graphite used in themud-laden fluid may bevaried within wide limits. That is, the requirement of constantcirculation of graphite within the bore of the well may be varied inaccordance to the frequency of complete drilling fluid changes,replacement thereof and renewals during operations.

There are various methods whereby the graphite can be applied to theequipment and at the same time improve the circulating drilling mud orfluid, all of which must ultimately conform to the requirement of thecirculation of the graphite through the well, to lubricate and applygraphoid surfaces to the successive changed bits and additional stringsof drill and casing pipe run in, as the bore is deepened.

To conserve against unnecessary loss or waste of graphite, continuous,interrupted of predetermined periods of circulation of the graphiteshall refer primarily to operations in wells where complete orsemi-renewals of the drilling fluid is often made during operations,where the drilling fluid is discarded after short use or stored to bere-claimed or re-processed for future use and new drilling fluidcirculated.

The graphite can successfully be used as follows:

1. By adding the graphite mechanically to the circulating mud-ladenfluid so as to circulate through the well and be unified therewith intoa single medium so as to lubricate and protect the drilling equipmentand generally improve the mud itself.

2. By-circulating the graphite in a continuous manner through the boreby means of a circulating drilling mud or fluid as the dispersingmedium.

3. By forming and using a "suspensoid drilling mud or fluid" forcirculation through the bore while operating the drillingequipment ofwhich the disperse phase is the solid graphite particles and thedisperse medium the drilling mud or fluid.

4. By adding graphite in varying proportions in the dry ground, hydratedor de-hydrated, or in combination with other materials at their point oforigin, distribution or at the well, and used thereafter as the integralor as a component part of the drilling fluid or mud circulating in thewell.

5. By adding the graphite to the components of the drilling mud or fluidby means of any of the mechanical or hand mixers generally used,

or add directly into the circuitous flow of the drilling mud whether itis in the open pit or in storage. a r

6. By spraying the graphite in dry blast or in a, colloidal or suspendedform to the mud or applying it to adhere to the equipment beforeentering the sub-surface or mouth of the bore, to be followed bycircuitous graphite applications by the mudding or flushing fluidscirculating through the bore of the well.

' 2,aaa,-s 7s colloidal, electric furnace graphite and graph- Where costof the material is to be considered, imported graphltes (Mexican phitesexcluded), principally fiake' and crystallines and certain classes ofamorphous (trade connotations) would not be used since-they are costprohibitive for the purposes of this invention, for they in no way showany advantages or benefits over domestic mined o'r manufacturedgraphites or Mexican graphites so as to warrant their use for the p pses of this invention, providing domestic graphite can be secured.

I have found that carbon allotrope graphites and domestic commercialamorphous graphite, mined in the United ,States, contain all theinherent properties and requisites, and when procitized carbon.Amorphous carbon is commercialessed in accordance to this invention, issuitable and adaptable for efllcient functioning and proper correlationand as fitting smoothly into all drilling mud and fluids to carry outthe objects of this invention.

As an 'example domestic amorphous graphite" is refined and processed bylevigating, grinding, riddling, and/or airfioating until the physicalproperties show a quantitative 80-85 percent graphitic carbon-that 98percent of the particles pass through screens of indicated 100 mesh, 80to 85 percent through 150 mesh, 35 to 40 percent through 200 mesh orfiner, free from grit or abrasive matter (tolerance of 5% or less) andof sp. g. 2.25-2.35. These figures may varied within wide limits. 7

As a second example, I make use of graphite of micro crystalline-likeminute particles of an intimate blend of levigated airfloated domesticand Mexican amorphous graphites and/or manufactured graphite levigated,ground and airfloated until the physical properties show a quantitativeof 85 percent graphitic carbon, when subdivided, reduced and fraotionedto come.

within the particle sizes, designated commercially as 300-325 mesh, sp.g.'-2.25-2.35 lu-v brlcous, highly u'nctuous and non-coalescent. Thesefigures may be varied within wide limits as well as the quantitative ofeach of the graphites within the blend and within the determinative asshown.

The following proportions have been found very satisfactory: 5% to 5%pounds of processed graphite added to each barrel (42 gallons- 5.6154cubic feet, oil country calculations, conversion factors) of circulatingdrilling mud or graphite per barrel may be'as low as 2% pounds.

After the drilling of each 100 cubic feet of bore,

fluid,. or 95 to 100 pounds of processed graphite as shown by the recordin the drilling log, the so quantitative determination of graphitecirculating should be evaluated by elutriation or through otherapparatusused at the well or in-the' laboratory for making tests ofquantity of solids in suspension. The graphite should then bereplenished to the amount pre-determined to care for the added equipmentand for the improvement of the functions of the added drillingfluidwithin the well as the bore deepens. V

Allotropic form of carbon is sometimes designated "Polymorph form.Natural graphite is commercially classified as fiake, crystalline, andamorphous graphite. Black lead and plumbago are mined, whereasmanufactured graphite are commercially classified as synthetic,artificial,

ly classified as carbon black, lampblack, wood charcoal, bone black andcoke. (Non-crystalline carbon.) "All graphites fundamentallyv are ofcrystalline formation. The amorphous carbon term is applied to acomparatively large variety of'carbonaceous substances which are notregarded as diamond or graphite. -Though originally intended to implythat these varieties of The properties of graphite differ widely fromThe those ofcarbon black for industrial uses. carbon black has but. a;minimum of lubricating and friction reducing value. Graphite of lessthan graphitic carbon is usually not 16-. garded ascommerciallubricating graphite be-v cause low in unctuous quality andlacking in an'inherent ability to'orient on metal surfaces and it has anexcess of. abrasive and organic matter. Such' graphit'es are generallyclassified for the foundry and paint industrieaetc. For

this invention, the highly unctuous and lubricating' graphitic carbonsare employed.

Carbon capable of orientation upon metal is preferred as an added:property;

This property of graphite isvery important. It enables the carbonmolecules to arrange themselves in crystaliine axial positionsupon metalsurfaces, thus' a good drilling mud usually has the followingingredients; and properties:

Solids per c ent 30-35 Water do 65-70 Viscosity seconds 25-35 Weight pound 72-82 pH value 8-10 Filtering properties ml. per hour 10-25 v Theamount of graphite to add to such a mudfiuid would depend upon a numberof factors, but as anexample:

Variables in the equation ofquantity of the allotropic form of carbon orits generic, "carbon allotrope graphite used as anadjuvant to thedrilling fluid depends uponmanyfactors. Itcan be computed on a slidingscalecalculated against the weight of a barrel of the circulatingdrilling fluid in relation to its pounds per cubicfoot and/or specificgravity (mud weight conversion tables of. relation-between specificgravity and mud-weights in oil country calculations, conversionfactors). v

dulating or to be circulated within the bore.

Solids and fluid, with or without applied admix- 2nd fa'ctor.When thesub-surface rotating assembly'is' devoid of graphoid surface.

3rd jactor.-When the sub-surface rotating assembly or any substantialpart thereofhad previ-I ous contact in operation or otherwise withcarbomud or graphiteand is already eraphoidsm'faced.

4th Jacton-When the casing is'run in the correction is made by lesseningthe amount of weighting materials which has been-added solely forincreasing the weight of the drilling mud.

Using a. conversion scale 01..readings from minus one per cent (-l%)minimum" to five per cent inclusive maximum" with two per cent (2%)indicator as the balance or poisepoint, it is possible to converge incalculations on the poise-point and care for the diverse factorsconnective or individually.

For example-Underthe combined factors 1-2-5, as set forth above, a 75pound per cubic foot drilling fluid or mud, pounds per gallon, sp.g.1.20 (a weight commonly utilized for drilling), to each barrel of suchfluid (42 gallons- 5.6154 cuuft.) there'would be added 2% to 3% (10 /2to 12 /2'=lbs.) of graphite i'orv thefirst 1000 lineal feet 'from the'spudding in of the well. Thereafter, the quantity is reduced (V2)one-half of one percent for each additional 1000 lineal feet drilleduntil a (1%) one percent proportion is reached. This percentage is thenused as average until completion of the well.

As a'seco'nd' example-Under combined factors 1--3-5, the normalrequirement would start at 2% (8 /2 pounds) of graphite and be reducedin the same proportion and manner for each 1000' lineal feetuntil 1% isreached. This proportion is then maintained until completion of thewell. These figures may be varied within wide limits, and tolerancesallowed where complete or partial changes of the drilling fluid inweight and character-ismade during operations to meet formation stratarequirements.

The slick lubricous allotropic form of carbon is inert and would not inany way be a detriment to a good drilling mud. The lubricous slick clipnature of the unctuous carbon energizes the la of thesluggiest mud flow,and accelerates the circuitous movement of the fluid, eliminatesnecessity of excessive pressure and induces better circulation. Theinfluence of the lubricous slick surfaces prevents flocculence oi: thephysical particles of the drilling mud or fluid. intensifies thehydraulic action of the jetted drilling mud or fluid and thus aids inremoving the cuttingsfrom the bit. It prevents the forming of cluster oraggregates of 'the cuttings rising to the surface within the drillingfluid, prevents formation or accumulation of dangerous gas pockets inthe ascending drilling mud, prevents blow outs, makes de-gassing of themud easier, lessens the strain on the drill pipe after the drilling mudhas packed and set while at rest in the bore and aids in re-starting thedrilling.

Having thus described my invention, what is claimed as new and desiredto be secured by Letters Patent is.

I claim:

1. In combination, an aqueous well drilling mud and graphitic carbon.

Further, it

' 2. In combination, an aqueous well drilling mud by the fact that it isa fluid to plastic mixture containing unctuous, non-coalescent graphiticcarbon particles of fine mesh.

6. An aqueous well drilling mud containing graphitic carbon having anailinity for metal surfaces and in which the carbon is of fine mesh ofapproximately 300 to 325.

7. The art of improving the lubricating of wells while being drilled byadding to the circulatory aqueous drilling mud thereof a proportion ofgraphite particles having orientation'and slickness characteristics as asuspensoid throughout the mass thereof.

8. The art of improving the lubricating qualities of aqueous welldrilling muds by spraying unctuous, metal adhesive type graphite in adry state onto the muds, and circulating the muds through the bore ofthe well and into contact with the lower end of the drill bit. whileoperating in the well.

9. The art of improving the lubrication of well drilling tools while inthe well and also the equipment connected with the mud circulatorysystem of the well by adding graphitic carbon to the aqueous drillingmud of the well, the graphitic carbon filling the pores of the metalparts contacted thereby.

10. The art of circulating an improved aqueous drilling mud through thehole of the well, drill ing stems, cutters and mud channels, etc.', of awell in which fine graphite particles are suspended in the mud, thegraphite, as a residue, adhering to the metal parts of the drillingequipment and functioning as a dry lubricant and protective graphoidsurfaces, the graphite penetrating to and remaining at points in thedrilling equipment inaccessible to other lubricants.

11. The art of reducing friction and equipment wear in the drilling ofwells by creating aboundary film of unctuous oriented graphite'particlesbetween the circulating drilling mud and subsurface drilling tools andequipment, and maintaining the film by continually circulating agraphitic treated mud in contact with the tools and equipment.

12. A lubricant and well drilling mud comprising substantially one tofive parts in a hundred of graphite and substantially ninety-five toninety-nine parts in a hundred of clays, and water added to form thefluid to plastic consistency desired.

13. An aqueous well drilling mud comprising about one to five percentgraphitic carbon, ninetyfive to ninety-nine percent mud formingingredients, and sufiicient liquid to allow the mud to flow underdesired pressures.

14, A well drilling circulatory substanceof a liquid to plasticconsistency containing a liquid, a. proportion of particles dispersedthroughout the substance, the particles comprising graphite of finemesh.

BARUCH CERF.

